sample method
Returns an Observable that, when the specified sample stream emits an item or completes, emits the most recently emitted item (if any) emitted by the source stream since the previous emission from the sample stream.
Example
new Observable.fromIterable([1, 2, 3])
.sample(new Observable.timer(1, new Duration(seconds: 1))
.listen(print); // prints 3
Implementation
Observable<T> sample(Stream<dynamic> sampleStream) =>
transform(new SampleStreamTransformer<T>(sampleStream));